1. Field of the Invention
The present invention relates to an information communication device, information communication system, and transmission control program for sending and receiving electronic data that requires copyright protection between a sending device and a receiving device.
2. Description of Related Art
The number of so-called digital information electric products is increasing and the popularity of these products is expected to spread with start of digital broadcasting. These products include such items as televisions compatible with digital broadcasting, digital VTRs, DVD players, hard disk recorders, and various other products that handle digital data and digital content.
One of the problems that must be addressed as these products became more widespread is the issue of copyright protection for the content. While digital data is advantageous in that it can be copied without degrading in quality, it has the disadvantage of being easy to copy illicitly.
Consequently, systems compliant with IEEE 1394, i.e., digital networks that connect digital AV (audiovisual) devices together, are provided with functions for authentication, key exchange, and data encryption.
Consider a hypothetical situation in which AV data requiring copyright protection is to be transmitted form a sending device to a receiving device. In such a situation, it is important for the copyright protection to be contrived in such a manner that an individual (or, in a broader interpretation, a family) can enjoy handling the AV data without being hindered by the copyright protection so long as the handling does not involve exchanging the AV data with other parties or the payment of listening/viewing fees or copyright royalties.
DTCP (digital transmission content protection) is a known system for providing copyright protection on networks. DTCP has become a de facto standard copyright protection method for use with IEEE 1394 and USB. With DTCP, authentication and key exchange processing is executed between the sending device and the receiving device with respect to the AV data or other content requiring copyright protection and the AV data is transmitted in an encrypted manner (see http://www.dtcp.com).
Generally, copyright protection in a transmission system involves transmitting AV data using the following processing steps. First, commands for sending and receiving AV data are issued between the sending device and the receiving device. For example, the receiving device issues the playback and (which is one of the AV control commands) to the sending device.
Next, the AV data is encrypted for copyright protection and transmission of the AV data from the sending device to the receiving device commences. Before or after the transmission, authentication and key exchange processing for the copyright protection is executed between the sending device and the receiving device. If the authentication and key exchange processing is successful, it becomes possible for the AV data encryption key to be shared by the sending device and the receiving device or for the sending device and receiving device to calculate an encryption key and the receiving device decrypts and plays back the received encrypted AV data. If the AV data transmission is conducted using an internet protocol (IP), various web applications can be linked and web browsers and other assets can be utilized so that various network configurations can be accommodated.
For this reason, an IP (more specifically, IPv4 or IPv6) is often used as the protocol for transmitting AV data that has been compressed using MPEG or the like. Still more specifically, such protocols as RTP (real time transport protocol) and HTTP (hypertext transport protocol) are used.
However, with an IP, a security problem arises because IP packets can be transmitted regardless of the specific network configuration. Consequently, there are IP technologies, such as VPN (virtual private network), for connecting remote IP networks together logically. When one of these technologies is used, IP packets can be transmitted between a home network of a person X in a district A and a home network of a person Y in a district B (which is physically distant from the district A) over the VPN or the like. In other words, the home network of the person X and the home network of the person Y can be operated as though they are a single home network.
Regarding copyright protection, copying and the like of AV data are allowed within the realm of individual enjoyment but other parties are not allowed to copy the AV data. However, by using one of the technologies just mentioned (e.g., VPN technology), it is possible to make the networks of different individuals appear logically as a single network (that is, it is possible to configure the networks as a single network) and there is the possibility that devices that violate copyright laws will became available.